The invention relates to a tool for multi-component injection molding of plastic toothbrush bodies for toothbrushes according to the preamble of claim 1.
The following is based on the supposition that with the tool not only a single toothbrush body can be injection molded, respectively, but that a tool is concerned with which simultaneously several toothbrush bodies can be injection molded.
For injection molding toothbrush bodies comprised of several plastic components, the initially injection-molded blank must be transferred into a further hollow mold space where further components are injection molded, in particular, in the area of the grip. In order to transfer the injection-molded blank of the first component into the hollow mold space for the second component, so-called turnover tools are known. This is to be understood such that a so-called turnover part is provided within one tool half which, after injection molding of the first component, is rotated by 180xc2x0 for injection molding of the second component, wherein this turnover part secures the injection-molded blank during the rotational movement.
The disadvantage resides in that this additional transfer device in the form of a turnover part contributes to limiting the hollow mold space for injection-molding of the first component. Inasmuch as the border line is in the area of the head of the toothbrush body to be injection-molded, a projecting burr can be formed there which is particularly undesirable in this head area of the toothbrush body because the person brushing the teeth with such a toothbrush can feel this burr in the mouth and can even be hurt by it in an extreme situation.
Based on this, it is an object of the invention to provide an improved tool for multi-component injection molding of plastic toothbrush bodies for toothbrushes which does not cause burrs in the area of the head of the injection-molded toothbrush body.
The technical solution is characterized by the features of the characterizing portion of claim 1.
The basic idea of the tool according to the invention for multi-component injection molding of plastic toothbrush bodies for toothbrushes resides in that the injection-molded blank comprising the first component is injection molded in a hollow mold space which is formed only by the two tool halves without the turnover device contributing to delimiting the hollow mold space. This prevents that, in particular, in the area of the head of the toothbrush body a circumferential burr results. By forming the hollow mold space for the first component exclusively by means of the two tool halves, this configuration includes that, for example, hole array pins project into the hollow mold space which can be removed again after injection molding of the first component. These hole array pins are considered part of the tool half. A further basic idea of the tool according to the invention resides in that for injection molding of the second component the transfer device essentially xe2x80x9cpicks upxe2x80x9d the injection-molded blank of the first component in that the turnover device is moved into the area of this injection-molded blank in order to pick it up in a suitable way and to transfer it subsequently into the hollow mold space for the second component. This transfer of the basic body into the additional injection molding station represents a technically simple possibility for manufacturing multi-component toothbrush bodies. Since the transfer device receives the injection-molded blank, this transfer device is formed as a cavity.
The further embodiment according to claim 2 suggests that the transfer device is linearly movable. The transfer device can be, for example, a pneumatic cylinder with stop position damping at both ends. With such a transfer device, the injection-molded blanks are transported linearly into the position for injection-molding the second component so that overall the transfer device performs a back and forth movement during an injection-molding cycle.
The further embodiment according to claim 3 suggests cross-section shapes of guides with which a technically simple and primarily reproducible movability of the transfer device is possible. In this connection, running plates can be provided, if desired, which are coupled with the transfer device.
A further preferred embodiment according to claim 4 suggests that the transfer device can be lifted off the correlated tool half. In this way, the injection-molded blanks can be initially removed from their cavities in a vertical transverse direction in order to subsequently transfer them into their position for injection molding the second component where the transfer device is then returned into its immersed position. Inasmuch as for the transfer device a T-shaped or L-shaped guide is provided, the transverse beam of the xe2x80x9cTxe2x80x9d or the xe2x80x9cLxe2x80x9d has a corresponding lifting stroke. For lifting the transfer device, a pneumatic short-stroke cylinder for lifting and lowering the transfer device can be provided.
The further embodiment according to claim 5 suggests a method as well as a constructive arrangement in order to first lift the injection-molded blank in an optimal way first from its cavity and then transfer it into the second cavity. The basic idea resides in that the transfer device grips the injection-molded blank from above and thus lifts it out of the cavity wherein the lifting movement can be assisted by tool ejectors in order to provide the necessary force for lifting.
According to a further preferred embodiment of the invention claim 6 suggests that the transfer device receives the head of the injection-molded blank. The advantage resides in that for injection-molding the second component the transfer device can continue to engage the head because generally no further component must be injection molded in this head area. Instead, additional components are injection-molded generally onto the area of the grip of the toothbrush body. However, in the case that the second component is to be injection-molded onto the head, the transfer device will grip the neck (or the grip) instead of the head.
The further embodiment according to claim 7 has the advantage that in a technically simple way the injection-molded blank can be taken from the cavity in that by a suction force pulling the injection-molded blank toward the transfer device, a force is generated which is large enough in order to overcome the securing force of the injection-molded blank in its cavity, wherein in this case moreover the lifting movement can be assisted by tool ejectors in order to provide the required force for lifting.
The further embodiment according to claim 8 is based on the fact that the injection-molded blank is secured for injection molding of the further component by the transfer device and, in this way, the cavity of this transfer device represents a partial cavity of the hollow mold space for injection molding of the second component. However, this only means that the transfer device defines the cavity for receiving the injection-molded blank, but that outside of the area of the transfer device between the injection-molded blank and the two tool halves additional cavities exist into which the second component is injection-molded. Accordingly, no plastic is injected into the transfer device, i.e., the transfer device will not come into contact with the injection-molded plastic. It is provided only as a negative cavity of the already injection-molded shaped elements.
The further embodiment according to claim 9 provides a possibility by means of which the finish-injection-molded toothbrush body can be secured within its cavity when the transfer device is extended for xe2x80x9cpicking upxe2x80x9d a new injection-molded blank. In this way, the finish-injection-molded product is secured by vacuum in the finish-injection-molding cavity, wherein the vacuum suction cups preferablyxe2x80x94alsoxe2x80x94engage the head of the toothbrush body. Accordingly, the mold insert in the head area can be provided with corresponding vacuum suction cups.
A first variant in the arrangement of the toothbrush body is suggested by the claims 10 and 11. In this arrangement, the heads of the toothbrush body are oriented toward the center because there the transfer device is located and this transfer device engages the injection-molded blank in its head area for the transfer process.
A second variant is suggested according to claim 12, where the toothbrush body is aligned in the transfer direction of the transfer device.
In minimal configuration of the tool, two components can be injection molded. Of course, it is also conceivable to injection-mold the toothbrush bodies with more than two components. In this case, the further embodiment according to claim 13 suggests that several stations for injection-molding of more than two components can be serviced by the transfer device.